Asian citrus psyllid control

Asian Citrus Psyllid

Basic Information

Life Cycle: Asian citrus psyllid (ACP), Diaphorina citri, mates and deposits eggs, that then hatch and pass through 5 nymphal instars. For more information on the biology, see ANR Publication 8205 Asian Citrus Psyllid or the homeowner pest note ANR Publication 74155 Asian citrus psyllid.

Host List: Asian citrus psyllid attacks citrus and closely related plants in the Rutaceae. See the California State Quarantine for the known hosts of ACP.

Damage: The psyllid attacks leaves and stems of citrus. When it feeds, it injects a toxin that causes twisting and death of the leaves. More importantly, it is an efficient vector of the bacterium Candidatus liberibacter asiaticus that causes Huanglongbing disease (HLB). This disease is one of the most devastating diseases of citrus; causing leaves to yellow, fruit to become bitter and eventually death of the tree. For more information on the disease, see ANR Publication 8218 Citrus Bacterial Canker Disease and Huanglongbing (Citrus Greening).

Distribution: The map shows the North American distribution of the psyllid (orange areas) and areas where both the psyllid + HLB disease are found (green areas). HLB is found in parts of Florida, Georgia, S. Carolina, Louisiana, Cuba, Belize, Nicaragua, Honduras and Mexico. In California, ACP was first found in 2008 in Imperial and San Diego counties and has since spread to Orange, Los Angeles, Ventura, San Bernadino and Riverside counties. It has been found primarily in yards, not commercial citrus. HLB was found in March 2012 in a tree in Los Angeles California in an urban situation.

Introduction – Distribution – Description and Identification – Life History – Damage – Host Plants – Survey and Detection – Disease Transmission – Management – Selected References

The Asian citrus psyllid, Diaphorina citri Kuwayama, is widely distributed in southern Asia. It is an important pest of citrus in several countries as it is a vector of a serious citrus disease called greening disease or Huanglongbing. This disease is responsible for the destruction of several citrus industries in Asia and Africa (Manjunath 2008). Until recently, the Asian citrus psyllid did not occur in North America or Hawaii, but was reported in Brazil, by Costa Lima (1942) and Catling (1970).

Figure 1. Adult Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by Douglas L. Caldwell, University of Florida.

In June 1998, the insect was detected on the east coast of Florida, from Broward to St. Lucie counties, and was apparently limited to dooryard host plantings at the time of its discovery. By September 2000, this pest had spread to 31 Florida counties (Halbert 2001).

Diaphorina citri is often referred to as citrus psylla, but this is the same common name sometimes applied to Trioza erytreae (Del Guercio), the psyllid pest of citrus in Africa. To avoid confusion, Trioza erytreae should be referred to as the African citrus psyllid or the two-spotted citrus psyllid (the latter name is in reference to a pair of spots on the base of the abdomen in late stage nymphs). These two psyllids are the only known vectors of the etiologic agent of citrus greening disease (Huanglongbing), and are the only economically important psyllid species on citrus in the world. Six other species of Diaphorina are reported on citrus, but these are non-vector species of relatively little importance (Halbert and Manjunath 2004).

Distribution (Back to Top)

Diaphorina citri ranges primarily in tropical and subtropical Asia and is reported from the following geographical areas: Afghanistan, Caribbean (Bahamas, the Cayman Islands, Jamaica, Dominican Republic, Cuba, Puerto Rico, plus interceptions from St. Thomas and Belize), Central America (Guadaloupe), China, Hong Kong, India, Indonesia, Malaysia, Mauritius, Mexico, Myanmar, Nepal, Pakistan, Philippine Islands, Reunion Island, Ryukyu Islands, Saudi Arabia, Sri Lanka, South America (Argentia, Brazil, Venezuela), Taiwan, Thailand, the United States and some of its territories (Halbert and Núñez 2004a)

The discovery of Diaphorina citri in Saudi Arabia (Wooler et al. 1974) was the first record from the Near East. Trioza erytreae also occurs in Saudi Arabia, preferring the eastern and highland areas where the extremes of climate are present, whereas Diaphorina citri is widespread in the western, more equitable coastal areas.

In the U.S. and its territories, this species is present in Alabama, Arizona, California, Florida, Georgia, Guam, Hawaii, Louisiana, Mississippi, Puerto Rico, South Carolina, Texas, and the U.S. Virgin Islands. In late May 2008, specimens were discovered in Jefferson and Orleans Parishes, Louisiana. On September 2, 2008, the psyllid was first detected in San Diego County, California. On October 27, 2009, the psyllid was discovered in Yuma County, Arizona. On April 21, 2010, surveys determined that the psyllid was present in the U.S. Virgin Islands (USDA 2010b).

As of June 2010, the following U.S. areas are quarantined due to the presence of the Asian citrus psyllid (USDA 2010c):

  • Alabama: entire state
  • Arizona: portion of Yuma County (USDA 2010b)
  • California: southern areas (USDA 2010a)
  • Florida: entire state
  • Georgia: entire state
  • Guam: entire territory
  • Hawaii: entire state
  • Louisiana: entire state
  • Mississippi: entire state
  • Puerto Rico: entire commonwealth.
  • South Carolina: southeastern area
  • Texas: entire state
  • Virgin Islands – entire Territory (USDA 2010b)

Description and Identification (Back to Top)

Adults: The adults are 3 to 4 mm long with a mottled brown body. The head is light brown, whereas Trioza erytreae has black head. The forewing is broadest in the apical half, mottled, and with a brown band extending around the periphery of the outer half of the wing. This band is slightly interrupted near the apex (in Trioza erytreae, band is broadest at middle, unspotted and transparent). The antennae have black tips with two small, light brown spots on the middle segments (in Trioza erytreae, antennae are nearly all black). A living Diaphorina citri is covered with whitish, waxy secretion, making it appear dusty.

Figure 2. Adult Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by Jeffrey Lotz, FDACS-Division of Plant Industry.

Nymphs: Diaphorina citri nymphs are 0.25 mm long during the 1st instar, and 1.5 to 1.7 mm in last (5th) instar. Their color is generally yellowish-orange. There are no abdominal spots, whereas in Trioza erytreae, advanced nymphs have two basal dark abdominal spots. The wing pads in Diaphorina citri are large, while Trioza erytreae has small pads. In Diaphorina citri, large filaments are confined to the apical plate of the abdomen (in Trioza erytreae, there is a fringe of fine white filaments around the whole body, including head).

Figure 3. Nymphal stages of the Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by David Hall, USDA.

Figure 4. The white waxy excretions of the nymphs are an indicator of the Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by Douglas L. Caldwell, University of Florida.

Figure 5. Adult female and nymphal instars of Asian citrus psyllid. Drawing by Division of Plant Industry.

Eggs: The eggs of Diaphorina citri are approximately 0.3 mm long, elongate, almond-shaped, thicker at the base, and tapering toward the distal end. Newly laid eggs are pale, but then turn yellow and finally orange before hatching. The eggs are placed on plant tissue with the long axis vertical to surface. Trioza erytreae eggs are laid with the long axis horizontal to surface.

Figure 6. Eggs of the Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by Douglas L. Caldwell, University of Florida.

Identifications having regulatory significance should be made by taxonomists with adequate reference materials. Psyllids as a group are most likely to be confused with aphids as these latter insects are common on tender citrus leaves. But adult psyllids are active jumping insects and aphids are sluggish. In addition, aphids usually have four- to six-segmented antennae, while psyllid antennae usually have 10 segments. Most aphids have cornicles on the abdomen, while psyllids lack cornicles.

Figure 7. Brown citrus aphid – adult wingless form.

Life History (Back to Top)

Eggs are laid on tips of growing shoots on and between unfurling leaves. Females may lay more than 800 eggs during their lives. Nymphs pass through five instars. The total life cycle requires from 15 to 47 days, depending upon the season. Adults may live for several months. There is no diapause, but populations are low in winter (the dry season). There are nine to 10 generations a year; however, 16 have been observed in field cages.

Damage (Back to Top)

Schwarz et al. (1974) listed four reasons why the symptoms of greening in Southeast Asia were often different from those in South Africa. These reasons included the more tropical climate of Asia keeping mature fruit green, citrus variety differences, differences in the heat tolerance of the vectors leading to different disease distribution in the grove, and differences in the virulence of the strains of the pathogen.

Figure 8. Feeding damage caused by the Asian citrus psyllid, Diaphorina citri Kuwayama, to citrus foliage. Photograph by University of Florida.

Figure 9. Huanglongbing or greening disease damage to a sweet orange tree. Photograph by Florida Department of Agriculture and Consumer Services.

Host Plants (Back to Top)

Mainly Citrus spp., at least two species of Murraya, and at least three other genera, all in the family Rutaceae.

Survey and Detection (Back to Top)

Nymphs: The nymphs are always found on new growth, and move in a slow, steady manner when disturbed.

Adults: The adults leap when disturbed and may fly a short distance. They are usually found in large numbers on the lower sides of the leaves with heads almost touching the surface and the body raised almost to a 30° angle. The period of greatest activity of the psyllid corresponds with the periods of new growth of citrus. There are no galls or pits formed on the leaves as caused by many other kinds of psyllids. The nymphs are completely exposed, while the nymphs of Trioza erytreae are partially enclosed in a pit. Citrus trees in advanced stages of decline are somewhat similar to those affected by tristeza. Field recognition of greening disease in Asia from symptoms alone is difficult. Very similar leaf symptoms may be caused by a wide variety of factors varying from nutritional disorders to the presence of other diseases such as root rots and gummosis, tristeza, and exocortis.

Capoor et al. (1974) described greening symptoms of citrus as trees showing stunted growth, sparsely foliated branches, unseasonal bloom, leaf and fruit drop, and twig dieback. Young leaves are chlorotic, with green banding along the major veins. Mature leaves have yellowish-green patches between veins, and midribs are yellow. In severe cases, leaves become chlorotic and have scattered spots of green. Fruits on greened trees are small, generally lopsided, underdeveloped, unevenly colored, hard, and poor in juice. The columella (the internal, central columnlike structure found in citrus and other fruits) was found to be almost always curved in sweet orange fruits and apparently is the most reliable diagnostic symptom of greening. Most seeds in diseased fruits are small and dark colored.

Figure 10. Twig dieback caused by Huanglongbing or greening disease to a Murcott tree. Photograph by Florida Department of Agriculture and Consumer Services.

Figure 11. Grapefruit damage caused by Huanglongbing or greening disease. Lopsided fruit are a symptom of greening disease. Note the extreme distortion of the columella, the central columnlike structure found in citrus and other fruits. Photograph by Florida Department of Agriculture and Consumer Services.

Disease Transmission (Back to Top)

Huanglongbing (HLB) is caused by a phloem-limited bacterium that has a true cell wall. There are at least three forms or species: Candidatus L. africanus causing African HLB; Candidatus L. asiaticus causing Asian HLB; and a new varient found in Brazil, tentatively called Candidatus L. americanus. Asian HLB is the bacterium found in Florida (Chung and Brlansky 2009). Capoor et al. (1974) reported a high percentage of transmission by tissue grafts. They found that 4th and 5th instar nymphs and adults could affect transmission. Diaphorina citri requires an incubation period before it can transmit the pathogen, which it retains for life following a short access feeding (15 to 30 minutes) on a diseased plant. Infectious nymphs retain their ability to vector the disease into adulthood. Adult psyllids can transmit the pathogen that causes greening after feeding for as little as 15 minutes, but transmission was low. One hundred percent infection was obtained when the psyllids fed for one hour or more. Capoor et al. (1974) indicated that the pathogen multiplied in the body of the psyllid and that there was an absence of transovarial transmission. They summarized differences between D. citri and Trioza erytreae in various aspects of greening transmission.

Figure 12. Symptoms of greening disease, Liberobacter spp, on citrus. Photograph by University of Florida.

Management (Back to Top)

Workers in India reported that Diaphorina citri can be controlled effectively with a wide range of modern insecticides. Injection of trees with tetracycline antibiotics to control greening disease was effective where the vector can be kept under control.

In countries where greening spread over long distances, it occurred because of the movement of infected and infested nursery stock. Only clean and healthy plants should be transported. In areas with low incidence of greening disease, any infected trees should be removed to prevent them from being reservoirs of the pathogen.

Natural enemies of Diaphorina citri include syrphids, chrysopids, at least 12 species of coccinellids, and several species of parasitic wasps, the most important of which is Tamarixia radiata (Waterston). Tamarixia radiata was introduced in Florida (intentionally) and the Rio Grande Valley of Texas (accidentally) (Michaud, personal communication).

Figure 13. Nymphs of the Asian citrus psyllid, Diaphorina citri Kuwayama, killed by the ectoparasitoid wasp Tamarixia radiata. Photograph by University of Florida.

In the United States and its territories, areas with Diaphorina citri are under quarantine (USDA 2010b). International quarantines, enacted by other countries, may also be placed on countries with Diaphorina citri.

Selected References (Back to Top)

  • Atwal AS, Chaudhary JP, Ramzan M. 1970. Studies on the development and field population of citrus psylla, Diaphorina citri Kuwayama (Psyllidae: Homoptera). Journal of Research Punjab Agricultural University 7: 333-338.
  • Bindra OS, Sohi BS, Batra RC. 1974. Note on the comparative efficacy of some contact and systemic insecticides for the control of citrus psylla in Punjab. Indian Journal of Agricultural Science 43: 1087-1088.
  • Capoor SP, Rao DG, Viswanath SM. 1974. Greening disease of citrus in the Deccan Trap Country and its relationship with the vector, Diaphorina citri Kuwayama. p. 43-49. In Weathers LG, Cohen M (editor). Proceedings of the 6th Conference of the International Citrus Virology, University of California, Division of Agricultural Sciences.
  • Catling HD. 1970. Distribution of the psyllid vectors of citrus greening disease, with notes on the biology and bionomics of Diaphorina citri. FAO Plant Protection Bulletin 18: 8-15.
  • Costa Lima AM. da. 1942. Homopteros. Insetos do Brazil 3: 1-327. Esc. Na. Agron. Min. Agr.
  • Halbert SE, Sun X, Dixon W. (2001). Asian citrus psyllid update. (no longer available online).
  • Halbert SE. (2006). Asian citrus psyllid – A serious exotic pest of FL citrus. (no longer available online).
  • Hall DG. 2006. A closer look at the vector: Controlling the Asian citrus psyllid is the key to managing citrus greening. Citrus & Vegetable Magazine 70 (5): 24-26.
  • Hall DG, Hentz MG, Adair Jr RC. 2008. Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves. Environmental Entomology 37: 914-924.
  • Husain MA, Nath D. 1927. The citrus psylla (Diaphorina citri, Kuw.) (Psyllidae: Homoptera) Memoirs of the Department of Agriculture India 10: 1-27.
  • Mangat BS. 1961. Citrus psylla (Diaphorina citri Kuway) and how to control it. Citrus Industry 42: 20.
  • Mathur RN. 1975. Psyllidae of the Indian Subcontinent. Indian Council of Agricultural Research, New Delhi. 429 pp.
  • Michaud JP. Personal communication. (19 October 2002).
  • Miyakawa T, Tanaka H, Matsui C. 1974. Studies on citrus greening disease in southern Japan. p. 40-42 In Weathers LG, Cohen M (editor). Proceedings of the 6th Conference of the International Citrus Virology, University of California, Division of Agricultural Sciences.
  • Moll JN, van Vuuren SP. 1977. Greening Disease in Africa. 1977 International Citrus Congress, Orlando, Florida, Program and Abstracts. 95 pp.
  • Pande YD. 1971. Biology of citrus psylla, Diaphorina citri Kuw. (Hemiptera: Psyllidae). Israel Journal of Entomology 6: 307-310.
  • Raychaudhuri SP, Nariani, Ghosh SK, Viswanath SM, Kumar D. 1974. Recent studies on citrus greening in India. p. 53-57. In Weathers LG, Cohen M (editor). Proceedings of the 6th Conference of the International Citrus Virology, University of California, Division of Agricultural Sciences.
  • Schwarz RE, Knorr LC, Prommintara M. 1974. Citrus greening disease in Thailand FAO Technical Document No. 93: 1-14.
  • USDA. 1959. Insects not known to occur in the United States. Citrus psylla (Diaphorina citri Kuwayama). No. 88 of Series. Cooperative Economic Insect Report 9: 593-594.
  • Wooler A, Padgham D, Arafat A. 1974. Outbreaks and new records. Saudi Arabia. Diaphorina citri on citrus. FAO Plant Protection Bulletin 22: 93-94.

Asian Citrus Psyllid Pest Profile

Public Service Announcement Video: Threat to California Citrus

The ACP feeds mainly on Citrus spp., at least two species of Murraya and several other genera all in the family of Rutaceae. Damage from the psyllids occurs in two ways: the first by drawing out of large amounts of sap from the plant as they feed and, secondly, the psyllids produce copious amounts of honeydew. The honeydew then coats the leaves of the tree, encouraging sooty mold to grow which blocks sunlight to the leaves. However, the most serious damage caused by ACP is due to its ability to effectively vector three phloem-inhabiting bacteria in the genus Candidatus Liberibacter, the most widespread being Candidatus Liberibacter asiaticus. These bacteria cause a disease known as huanglongbing, or citrus greening. In the past, these bacteria have been extremely difficult to detect and characterize. In recent years, however, DNA probes, electron microscopy, and enzyme-linked immunosorbent assay tests (ELISA) have been developed that have improved detection. Symptoms of huanglongbing (HLB) include yellow shoots, with mottling and chlorosis of the leaves. The juice of the infected fruit has a bitter taste. Fruit does not color properly, hence the term “greening” is sometimes used in reference to the disease. Huanglongbing is one of the most devastating diseases of citrus in the world. Once infected, there is no cure for the disease and infected trees will die within ten years. The once flourishing citrus industry in India is slowly being wiped out by dieback. This dieback has multiple causes, but the major reason is due to HLB. In California, the disease has only been found in residential areas of Los Angeles and Orange counties.

Asian Citrus Psyllid & Citrus Greening or HLB

What is it?

A tiny insect, the Asian citrus psyllid (ACP) is threatening citrus trees around the world, including orange, grapefruit, tangerine, kumquat, lime, lemon and other varieties of citrus.

ACP has needle-sharp teeth that it uses to pierce plants and extract the juices. It prefers to feed and reproduce on the new leaf growth of citrus and closely related plant species.

ACP damages new growth because it injects toxins into plant tissues while it feeds. This causes curling, distortion and blackening of young leaves. Insect populations increase during periods of active plant growth. The tiny adults look like aphids—measuring about ⅛inch—and characteristically feed with their tails end raised at a distinct 45 degree angle from the leaf. Their bodies are grayish-tan with brown markings and mottled brown wings. The extremely small nymphs are bright orange-yellow and exude a distinctive trail of white, waxy material.

What is the threat?

In addition to the damage it causes while feeding, ACP often carries and transmits a disease called citrus greening, also known as huanglongbing (HLB).

Citrus greening or HLB is considered one of the most devastating diseases for citrus trees, and there is no known cure. ACPs do not always carry the disease, but the disease can only be spread by the insect or through contact with infected material. Symptoms of the disease include yellowing growth and uneven ripening, producing lopsided fruit with a bitter taste. It can take up to three years for HLB symptoms to be visible in a citrus tree. The disease can kill trees within three to five years.

The disease has devastated commercial citrus industries around the world, causing billions of dollars in damage. In Florida alone, tens of thousands of acres of citrus trees have been removed. Whether in orchards or backyards, citrus greening threatens the very survival of citrus in the United States and around the world.

Where is it?

Most states where citrus can be grown outdoors have quarantines for ACP and/or HLB. They include Alabama, Mississippi, Louisiana, Texas, Hawaii, Arizona, California, Florida, Georgia, South Carolina and Louisiana. For a map and more information on quarantines, visit saveourcitrus.org.

What can you do?

The only way to prevent the spread of citrus greening is to control ACP. Since citrus trees are so popular and widely planted in gardens, homeowners are on the frontlines of this important battle.

  • Know and follow quarantine rules in your state, especially when it comes to purchasing and moving citrus trees (including citrus relatives), fruit and plants parts.
  • Purchase plants only from reputable nurseries and garden centers.
  • Do not move plants, fruit and plant parts out of your area and especially across state or international borders.
  • Consume fruit on your property.
  • Dry or double bag plant clippings prior to disposal.
  • When grafting trees, only use registered budwood that comes with source documentation.
  • Cooperate with officials who need to inspect or treat citrus trees in your yard or neighborhood.

Become familiar with signs of ACP and citrus greening. Inspect your citrus trees monthly and report suspected psyllids or symptoms of citrus greening to proper authorities. Collect samples of any suspected ACP damage. Seal the sample in a plastic bag and call your county agricultural commissioner. If you live in California, call the California Department of Food and Agriculture Pest Hotline at 800-491-1899. In Florida, call the Division of Plant Industry at 800-282-5153.

For more information about possible preventative measures and potential treatments, please contact your local extension service, certified arborist or professional nursery.

Other Resources

Saveourcitrus.org can provide a wealth of information on ACP and citrus greening as well as other insects and diseases that threaten citrus. It will direct you to local information about quarantines and who to contact if you suspect ACP or citrus greening.

Californiacitrusthreat.org is another valuable resource on all things ACP and citrus greening.

Citrus Trees: Move It AND Lose It

Help Save Our Citrus — visit www.saveourcitrus.org or follow us on Facebook and Twitter.

Soon, citrus producing states across America, including Arizona, California, Florida, Louisiana and Texas, will be full of fresh citrus. But gone are the days of sharing the fruit trees or seeds with friends and family out of state or even in the next county. It’s no longer as simple as packing it up and shipping it, or buying a citrus tree at a road side stand to bring home.

You’ve heard the saying “move it or lose it.” When it comes to citrus trees, it’s “Move It AND Lose It.” When you move citrus trees, you risk losing America’s citrus altogether – think breakfast with no fresh oranges, grapefruit or even juice.

Moving citrus trees is the fastest way that citrus diseases are spread. Four serious citrus diseases found in the United States include Huanglongbing (also known as citrus greening or HLB for short), citrus canker, citrus black spot and sweet orange scab. Learn more about each disease by visiting the What Are the Diseases section of the Save Our Citrus website.

When infected trees, fruit, clippings, equipment or even workers are moved to a new area, the disease comes with them. It’s not just commercial citrus that is susceptible to these diseases. Homegrown citrus trees can easily become infected and spread disease.

Move It AND Lose It: Five Things You Need to Know

  1. Be Aware of Quarantines. Knowing where quarantines are is key to preventing the spread of disease. For example, if your county is under quarantine for both the Asian citrus psyllid and citrus greening, this means that citrus cannot leave these counties. No citrus plants, fruit, equipment or items made with citrus (such as floral arrangements, wreaths, potpourri or seasonings like kaffir lime leaves) may be moved from quarantined areas. Not only are you risking spreading citrus diseases by transporting citrus outside of these areas, but it’s also against the law. Check our quarantine map to learn what areas are under quarantine.
  2. Inspect Citrus Plants Regularly for Diseases and Insects. Check citrus plants for signs of Huanglongbing and other citrus diseases. If you detect an infected plant, report it immediately.
  3. Keep Homegrown Citrus at Home. Help reduce the spread of citrus diseases by not moving your homegrown citrus plants or fruits. Even if a tree looks healthy, don’t move it. This is the simplest yet most important thing for all Americans to do to protect our citrus.
  4. Check Citrus Plant Suppliers. Be a savvy buyer. Only buy citrus plants from a reputable, licensed nursery. Commercial fruit packers, Internet shippers and roadside vendors within regulated states should be able to show that they are in compliance with the federal quarantine. Before you buy, ask the vendor if their product is in compliance. If you buy a plant that is disease-free, you’ll have a much healthier, more productive tree.
  5. Avoid Fines and Penalties. If you knowingly purchase citrus trees in violation of quarantine regulations and requirements, the penalties could range from $1,100 to $60,000 per violation. If you suspect citrus trees are being moved improperly, report your concerns to your USDA State Plant Health Director’s office; you can find contact information online at www.aphis.usda.gov/aphis/banner/contactus.

Thank you for doing your part to stop the spread of citrus diseases. To learn more about the Save Our Citrus campaign, visit www.saveourcitrus.org or follow us on Facebook and Twitter.

Category/Topic: Animals Plants

Write a Response

Duane Runciman Sep 23, 2014

The level of concern of Citrus Greening is reported in a number of articles, however our company (UK based – Organic chemicals) carried out 2 live psyllid trials and had 100% success on sterilising the off spring of the psyllids and yet getting the research people to give us the time of day is near on impossible. This is ridiculous to think of the millions of your tax payer $$ being spent on various research and we have something worth pursuing but because we are not a US based research institute we don’t get the time of the day. We spent a mere 4,000 GBP studying this with a fully safe / non toxic / organic product and had 100% success in controlling the spreading agent using the same vector (what more could you want than spreading of clean insects to breed out the bacteria) and no one pays 1 iota of attention …shame on the Citrus Grower research organisations and your government agencies. We will keep pursuing this as it is a clean, organic and sustainable solution worth further study to prove the point.

Deb Gateley Dec 30, 2015

What about the spread of disease by mail? Years ago, mail processing plants had Ag dept inspection stations. There seems to be no inspections any longer. I work inside a post office in the central valley of CA, and customers are continually mailing citrus in our flat rate boxes to all corners of the US. I try to dissuade them, but I’m the only one it seems. Can the postal service get some back up on not mailing backyard fruit? USPS should be adhering to Ag restrictions, but the rules are very unspecific. Thank you

John E Burchard Sep 04, 2016

This is antique (it’s now September 2016). What is the current status? I live in the Central Valley of California (I’m a Water District general manager) and in this immediate area we have no citrus (too cold in winter on the valley floor, citrus are on the slopes). We have alfalfa and (now, all of a sudden) pistachios. Nowhere near enough water to support all that – but that’s a different rant. I would be interested in growing kaffir limes for leaves and perhaps fruit – and also curry tree leaves. How to get uninfected plants?

Dan c. Nov 27, 2016 Organic Trees Dec 28, 2016

I love Citrus trees. Citrus trees should be planted in a sunny and wind-protected area.Trees can be planted at any time duration. However, spring is the best time.To treat infected area, Clean-up and remove all leaf debris under the tree. Prune the lower branches from the tree, those that are more than 2 feet from the ground. Then spray with a fungicide such as Agri-Fos or Captan.

BKBardi Apr 03, 2017

Hello! Your links above are no longer working. 🙂 Good article as I’m thinking of growing a Kaffir lime tree in my home (indoors) for seasoning and having fresh leaves available when needed by freezing them. Is there a restriction on indoor grown Kaffir lime and moving it? Or, do I need to bag it and have it quarantined before moving to a restricted area (Alabama to…??? – anywhere but here GS Civilian) – and even though I’d be keeping it indoors. Thanks in advance for any info you can provide! USDA – Love the work you do every day!

Diane Baxter Jun 01, 2017

Is it safe to buy a citrus tree from Home Depot with a tag that says”Do not move in or out of a quarantined area? This is in Los Angeles County.

Ben Weaver Jun 01, 2017

@Diane Baxter – Hi Diane, yes, you can buy a citrus tree from Home Depot. However, the tag indicates that the tree is currently being purchased within a quarantine area. A quarantine is an area where the movement of plants is regulated and it would be a violation of federal regulations to leave the quarantine area with the plant. You can find information about the current quarantine boundaries here: https://www.cdfa.ca.gov/plant/pe/InteriorExclusion/quarantine.html. The quarantines that apply to citrus in California are for the Asian Citrus Psyllid (ACP) and Huanglongbing (HLB) or citrus greening. Citrus is also a host for many fruit flies.

Peter Karastamatis Oct 08, 2017

I frequently observe citrus trees for sale at Home Depot and Lowe’s that have green fruit that appears to have either canker or greening disfiguration on the fruit. The employees tell me their products are approved for sale by inspectors. Recently I purchased and planted very young Persian lime and Meyer lemon young trees. The lime had a fruit on it the size of a golf ball and their were two others that were slightly smaller and forming. They were clean at purchase. Within 4-6 weeks the larger fruit showed small pock marks similar in appearance to canker spots. A few weeks later the affected area spread to two thirds of the fruit surface looking exactly the same as pictures of canker diseased fruit. Is it possible the trees contacted disease while planted that showed on already forming fruit? There are no other signs of greening, canker or leaf miner activity on the tree or leaves. Any suggestions? My feeling is the box store sold an infected tree because I continuously see these possibly diseased fruits on display at both stores. Any suggestions would be appreciated.

Irene F Kilstrom Jun 02, 2018

I recently came home from vacation and found my two lemon trees (in Pots) tagged and quarantined. I wondered if it is my whole neighborhood that was quarantined or just how it was known that I had two trees in my backyard. I would think that I should have been notified either by a knock on the door (I was not home) or a note left that it was done and that they had been on my property.

Ben Weaver Jun 05, 2018

@Irene F Kilstrom – USDA staff and our State agriculture department partners conduct periodic inspections throughout the year to monitor the health of citrus trees in and around citrus-related quarantine areas. You can see where there are citrus-related quarantines at www.aphis.usda.gov/aphis/resources/pests-diseases/save-our-citrus/soc-resources/soc-quarantine-info. Early detection is the most cost effective method to prevent citrus disease outbreaks with minimal impact on homeowners, the environment, economy, and U.S. agriculture.

Citrus Fan Jul 28, 2018

In 1.Be Aware of Quarantines. it states “Check our interactive quarantine map to learn what areas are under quarantine.” The word “our” is misleading since it suggests that the map and associated link is to a USDA managed page, but the link goes to a NON-USDA site. Also, the map is non-functional or non-existent. Please fix this.

Ben Weaver Aug 01, 2018

@Citrus Fan – Because this blog post is several years old, USDA no longer supports the website and the mapping element described in this blog post. Now, you can find citrus information by logging onto www.aphis.usda.gov/aphis/resources/pests-diseases/save-our-citrus. To find more information about APHIS’ citrus health programs, you can go to our Citrus Health Response Program page. For information about quarantines in specific states, please click on the specific citrus pest you are interested in on that page.

Debbie dean Jul 22, 2019

I am moving from Washington state to Arizona. Can I take my lime tree? I will be passing through Oregon, Idaho, Utah and nevada .

Theresa Dec 01, 2019

Still confused. Can I ship my Florida homegrown grapefruit to family members in North Carolina and Tennessee?

Ben Weaver Dec 05, 2019

@Theresa – thank you for your comment. The entire state of Florida is under quarantine for citrus greening disease, Asian citrus psyllid, citrus canker and sweet orange scab. A relatively small area of southwest Florida in adjoining areas of Hendry and Collier counties is under quarantine for citrus black spot. Due to these quarantines, USDA APHIS prohibits the movement of homegrown citrus out of the state of Florida. This means that homegrown grapefruit from Florida cannot be shipped or hand carried to North Carolina or Tennessee.

First spotted in Palm Beach County, Florida in 1998, the Asian citrus psyllid is rapidly becoming a threat to citrus and other close relatives throughout select regions of the United States. Its movement is being closely tracked by the USDA and Cooperative Extension offices as a result. First signs of the psyllid and/or Citrus Greening Disease (Huanglongbing) should be reported to your local county extension service. Much of the spread of the Asian citrus psyllid is attributed to the transportation of infested nursery plants, so close inspection of desirable plants should be done before purchase and transport. Quarantines have been and continue to be put in place where the pests are identified. While the psyllid can cause significant cosmetic damage to plants, it is the disease the psyllid vectors, called Citrus Greening, that is most threatening to orchards, nurseries and home growers alike.

Asian Citrus Psyllid Life Cycle:

Eggs are identified by their bright yellow-orange color and almond shape. They are often found in the creases of feather flush leaves or on the tips of growing shoots; however, the number of eggs laid depends on the host plant and seasonality as ample new growth is needed for nymphs to feed and mature. Eggs hatch in as little as 4 days varying with warmer or cooler temperatures. Asian citrus psyllids mature through five nymph stages before reaching adulthood and will be concentrated on or near new growth sites. Nymphal stages share similar coloring to the eggs and feed exclusively on new growth as mature leaves harden to the point feeding is impossible. Once they reach adulthood, Asian citrus psyllids are brownish in color and feed on young and old foliage. Adult life spans range from 1-2 months and are heavily influenced by temperature and host due to the fluctuations in flush timing and frequency. Under optimal conditions, the Asian citrus psyllid can complete 30 generations per year.

Damage Symptoms & Identification:

Asian citrus psyllids damage resembles that of other psyllid species with leaf curling/twisting and reduced plant vigor common; however, the paramount concerns surrounding the Asian citrus psyllid are the transmission of Huanglongbing disease (Citrus Greening disease) and the stunting of new growth due to the damage inflicted by nymphs. The nymphs inject a toxin into the leaf tissue as they feed causing leaf curl. In high population areas, the injected toxin burns new growth and can kill new shoots. Huanglongbing disease shows up as asymmetrical yellowing of leaves in a section of the canopy, which differs from the more symmetrical yellowing along veins caused by nutrient deficiencies.

Asian citrus psyllid nymphs excrete honeydew while feeding like aphids, whiteflies and some species of scale. This sticky substance accumulates on leaves and promotes the growth of fungal diseases like sooty mold. The high sugar content of the honeydew often draws the attention of ants that will protect pest colonies that produce it.

Monitoring & Controlling Asian Citrus Psyllid:

Notify your local county extension service immediately if Asian citrus psyllids are detected. The following control measures are for the Asian citrus psyllid only. Once a tree is infected with Huanlongbing disease, there is no cure.

  • If you are in a region where the Asian citrus psyllid is a known pest or is being monitored by authorities, do your part and set up traps in your growing space. There are specialized Asian Citrus Psyllid Traps that come with a pheromone lure and are useful in a backyard or orchard setting.
  • Inspect the new growth of any citrus you have for signs of psyllid damage: waxy deposits, honeydew, sooty mold, ant activity and twisted leaves. The presence of adults and/or egg masses indicates a need for active control needs to be taken.
  • Apply Grandevo and/or Venerate XC starting early in the growing season to kill nymph and adult psyllids. Both of these OMRI listed biopesticides limit impacts on beneficial insects in the growing area.
  • If Huanglongbing disease is identified, chemical control should be taken in addition to quarantine measures as beneficial insects do not provide adequate control to halt the spread of the disease.
    • Horticultural Oils will suppress psyllid feeding by making it more difficult to pierce the leaf surface and coating psyllids they come in contact with. Use JMS Stylet Oil to limit risk of phytotoxicity.
    • Neem Oil is a contact insecticide and acts as a feeding/growth inhibitor to all stages of psyllids. In addition, neem helps to control fungal diseases.
    • In the case of severe infestation, consider Pyrethrin and/or Azadirachtin insecticides. They can be used as standalone sprays or in an alternating spray program depending on your needs.
  • Inspect all plants and fruit before transporting them. If pests or disease symptoms are found, dispose of the affected material immediately.

Controlling Asian Citrus Psyllids & Citrus Greening Disease

Few pests pose a more daunting threat to citrus than the tiny Asian Citrus Psyllid (ACP), a potential carrier of a disease that could ravage the citrus industry and wipe out trees in home gardens. Because it can spread the bacterial disease called Citrus Greening Disease, aka Huanglongbing (HLB), this insect has sparked intensive quarantine and eradication efforts just about anywhere citrus can be grown outdoors.

What Is This Insect?

ACP is a small insect with needle-like mouthparts used to pierce plants and suck out the juices. The tiny adults look like aphids, measuring about 1/8 inch and characteristically feeding with their tail end raised at a distinct 45 degree angle from the leaf. Their bodies are grayish tan with brown markings and mottled brown wings. The extremely small nymphs are bright orange-yellow and exude a distinctive trail of white, waxy material.

According to the U.S. Department of Agriculture, ACP prefers to feed and reproduce on the new leaf growth of citrus and closely-related plant species, such as:

  • Orange Jessamine (Murraya paniculata)
  • Sweet Orange and Mandarin Orange
  • Lemon
  • Lime
  • Tangerine
  • Grapefruit
  • Kumquat

ACP adults and nymphs damage new growth because they inject toxins into the citrus plant or tree while they feed. This causes curling, distortion and blackening of young leaves. Insect populations increase during periods of active plant growth. ACP often carries and transmits a disease called Citrus Greening Disease, aka huanglongbing (HLB). As they feed and inject toxins to distort plant leaves, ACP can infect the citrus host simultaneously.

Citrus Greening Disease

Citrus Greening Disease, or HLB, is considered one of the most devastating citrus diseases, and there is no known cure. ACPs don’t always carry the disease, but the disease can only be spread by the insect or through infected propagating material. Symptoms of the disease include yellowing growth and unevenly ripening, lopsided fruit with a bitter taste. It can take up to three years for Citrus Greening Disease symptoms to be visible in a citrus tree. Infected trees produce inedible fruits and eventually die. Citrus trees infected with the disease must be destroyed.

The disease has devastated commercial citrus industries around the world, causing billions of dollars in damage. In Florida alone, tens of thousands of acres of citrus trees have been removed. Whether grown in orchards or backyards, Citrus Greening Disease threatens the very survival of citrus in the United States and around the world.

Where Is ACP Found?

Most states where citrus can be grown outdoors have quarantines for ACP and/or Citrus Greening Disease. They include Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, Texas and South Carolina. Go to saveourcitrus.org for more information and a map of quarantine areas.

You Can Help Stop The Spread

The only way to prevent the spread of Citrus Greening Disease is to control ACP. Since citrus is such a popular and widely-planted garden tree, homeowners are on the front lines of this important battle. Here’s how you can help:

  • Know and follow quarantine rules in your state, especially when it comes to purchasing and moving citrus trees (including citrus relatives), fruit and plant parts.
  • Only purchase plants from reputable nurseries and garden centers.
  • Do NOT move plants, fruit or plant parts out of your area, especially across state or international borders.
  • Consume fruit on your property.
  • Dry or double bag plant clippings prior to disposal.
  • When grafting trees, only use registered budwood that comes with source documentation.
  • Cooperate with officials who need to inspect or treat citrus trees in your yard or neighborhood.
  • In quarantined areas, protect your citrus trees against ACP with properly labeled foliar sprays and/or a systemic insecticide soil-drench applied prior to the flush of new growth in late summer or early fall, or in spring after bloom. Carefully follow label instructions.
  • BioAdvanced™ Fruit, Citrus & Vegetable Insect Control* offers insect protection** all season long. Best of all there’s no spraying! Simply apply it around the base of your tree for systemic protection from the roots to the tip of every leaf.

What To Do If You Think You Have ACP

Be familiar with signs of ACP and Citrus Greening Disease. Inspect your citrus trees monthly. If they are showing signs of ACP activity or any symptoms of Citrus Greening Disease:

  • Go to SaveOurCitrus and click on the “Report It” button. Then follow the instructions.
  • Collect damaged samples, seal the samples in a plastic bag, and report it to your county agricultural commissioner immediately.
  • In California, call the California Department of Food and Agriculture Pest Hotline at (800) 491-1899. For more information, visit Californiacitrusthreat.org
  • In Florida, call the Division of Plant Industry at (800) 282-5153.
  • In other areas, contact your local Cooperative Extension System office or your local agricultural commissioner.

Other Resources

SaveOurCitrus can provide a wealth of information on ACP and Citrus Greening Disease, as well as other insects and diseases that threaten citrus. It will direct you to local information on quarantines and on whom to contact. Californiacitrusthreat.org is a valuable resource on all things ACP and citrus greening.

*Not for sale, sale into, distribution, and or use in Nassau, Suffolk, Kings and Queens counties of NY. Reclassified as restricted use in CT & MD.

**Listed insects.

Photo Credit: H.D. Catling, Bugwood.org

Biological Control of Asian Citrus Psyllid in Dooryard Citrus and Ornamentals

Tiny Insect Placing Florida Citrus in Jeopardy

Citrus trees in Florida are under attack from a recently introduced major citrus pest known as the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. ACP is a tiny mottled brown insect about the size of an aphid that feeds on all varieties of citrus and a few closely related ornamental plants in the family Rutaceae such as Chinese box orange, Indian curry leaf and orange jasmine. The psyllid damages citrus directly by feeding on new leaf growth (flush) but, more importantly, transmits a plant pathogenic bacterium, Candidatus Liberibacter asiaticus (CLas), that is responsible for a destructive citrus disease known as huanglongbing (HLB) or citrus greening disease. Asian citrus psyllid and HLB were first found in Florida in 1998 and 2005, respectively; and the disease has put the state’s citrus industry in serious danger.

The psyllid acquires the bacteria when it feeds on bacteria-infected plants; and the disease spreads when a bacteria-laden psyllid flies to a healthy plant and injects the bacteria into it as it feeds. HLB causes dieback of foliage and roots, stunted growth, discoloration of leaves, distorted and bitter fruit, and tree death in as little as five years. There is no known cure. The only way to protect trees and prevent the spread of HLB is by controlling psyllid populations and destroying infected trees.

ACP/HLB Management Options

In Florida’s citrus groves, management of HLB depends primarily on controlling ACP with regular pesticide applications. However, insecticides are not used to control ACP everywhere in Florida, and anywhere ACP populations are not controlled can serve as a reservoir for the insect and the disease, which can then spread and threaten commercial citrus groves. Many homeowners rarely use pesticides and have dooryard citrus trees and susceptible ornamentals that can support large populations of ACP. Indeed, dooryard citrus and orange jasmine hedges are especially problematic because they are often trimmed and irrigated, which induces frequent leaf flushing that is used by ACP for egg-laying and facilitates population increases.

Adult psyllids are known to move frequently between host plants in search of new growth, can fly over a mile, and move even greater distances in strong winds. Therefore, it is important that homeowners monitor their citrus trees and susceptible ornamentals for ACP and take action to control this serious pest either through the use of pesticides or an alternative method known as biological control. Biological control is an environmentally sound and effective means of reducing or mitigating pests and pest effects through the use of natural enemies.

For those interested in chemical control, current insecticide guidelines for ACP management are provided by the University of Florida. For those interested in biological control, the Florida Department of Agriculture and Consumer Services (FDACS) can assist by providing biocontrol agents for release on your property. Further information on our ACP biological control program including how to obtain insects for release can be found below. Natural enemies of ACP can be especially useful for controlling ACP on citrus trees and ornamentals. Lady beetles, syrphid fly larvae and lacewing larvae are especially good natural enemies of ACP. In addition, the FDACS has a program that mass rears and releases millions of tiny parasitic insects known as Tamarixia radiata (Waterston) throughout Florida in an effort to combat ACP and HLB in areas without effective pesticide programs.

Tamarixia radiata attacks and kills ACP, and has no negative impact on any organism other than psyllids. For homeowners, releasing these parasitoids on your property can benefit your citrus trees and those of your neighbors as the parasites reproduce and spread. Moreover, helping to control ACP in your neighborhood can provide relief for nearby commercial citrus growers by removing additional sources of ACP and HLB.

If you are not a commercial citrus grower and would like to request parasitoids for release on your property to reduce ACP populations in citrus or ornamental plantings, please fill out the Tamarixia Release Form. Forms will be emailed automatically to FDACS ACP biocontrol project coordinators. Your information is kept confidential. Supplies of Tamarixia are limited, but program staff will respond to all inquiries and send parasites to as many requesters as possible. Parasitoids will be shipped overnight at no cost with instructions for releasing the insects, which is fun and easy and can be extremely important for protecting our citrus industry.

ACP Biological Control

Shortly after the discovery of ACP in Florida in 1998, Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), a highly specific parasitoid of ACP, was imported from Southeast Asia and released in Florida citrus groves. Tamarixia radiata has been reported to effectively suppress ACP populations in locations such as Reunion Island, India, Puerto Rico and Guadeloupe. After release, the parasitoid quickly established in Florida and now occurs widely throughout the state and causes varying levels of ACP control.

Tamarixia radiata females lay an egg on the ventral surface of the ACP nymph. The resulting larval wasp consumes the body fluid of the ACP nymph, eventually killing it and turning the empty psyllid casing into a “mummy” where the wasp pupates and develops to adulthood. Adult wasps chew an exit hole through the dorsal surface of the mummy, emerge, and fly off to attack other psyllids. Female Tamarixia also destroy ACP nymphs by feeding on them. Over her lifetime of approximately 28 days, a T. radiata female is capable of killing over 500 ACP nymphs.

Host Plants of Asian Citrus Psyllid

In addition to citrus, common ACP host plants include the Chinese box orange (Severinia buxifolia), Indian curry leaf (Murraya koenigii) and orange jasmine (Murraya paniculata =exotica). Orange jasmine is widely grown as an ornamental hedge plant in Florida and is regarded as one of the preferred host plants of ACP. After HLB was found in Florida, concern developed that orange jasmine grown in urban and commercial areas might contribute to larger area-wide Asian citrus psyllid populations, and be problematic for nearby commercial citrus groves. Murraya sp. including orange jasmine became regulated in 2007 which, under Rule Chapter 5B-63 of the Florida Administrative Code (F.A.C), effectively shut down movement and sale of orange jasmine within Florida. The rule was instituted in response to research showing that past distribution of the plant to large box stores was a major contributing factor to the spread of ACP throughout Florida.

It is still legal to grow orange jasmine in Florida, but only under the same restrictions that apply to citrus including confinement in an approved screened facility. To our knowledge, there are no orange jasmine growers remaining in Florida. However, there is no rule requiring the removal of established plantings in Florida. If you own orange jasmine plantings and live near dooryard or commercial citrus you may consider the removal of these plants to reduce ACP populations in your area.

Asian Citrus Psyllid

ACP has a native range in tropical and subtropical Asia and can now be found throughout many tropical and subtropical fruit-producing regions of the world. Psyllid feeding activities cause direct damage to trees, but more importantly ACP is a vector of Candidatus Liberibacter species, bacterial pathogens responsible for citrus greening disease. Adult ACP measure 2 to 4 mm long and are a patchy brown and tan color. Psyllid adults reach reproductive maturity two to three days after they emerge as adults and are capable of laying over 800 eggs in a lifetime.

Yellowish-orange, tear-shaped eggs are laid on the unfolded leaves, flower buds, leaf axils and the tips of newly expanding flush. Nymphs begin to feed on sap from the phloem of soft new flush and may feed on harder stems as they mature. Adults are capable of feeding on mature hardened leaves in the absence of new flush. While resting or feeding, adults generally sit on the undersides of leaves where they maintain their body at a 45° angle relative to the leaf surface.

HLB Infected Tree and Fruit Symptoms

Huanglongbing means “yellow dragon disease” or “yellow shoot disease” in Chinese. The name comes from the yellow shoots that are early symptoms of the disease. Additional typical symptoms include blotchy (asymmetric) mottling of leaves, chlorosis resembling zinc deficiency, thinning canopies, leaf drop and twig dieback. Symptomatic fruit are small and lopsided with small, dark aborted seeds and discolored vascular bundles in the fruit axis. Young citrus trees that become infected generally decline and die faster than older trees. Replanting trees and getting them into production without contracting HLB is difficult even under intensive ACP insecticide programs. Florida citrus acreage has been significantly reduced in recent years due to HLB.

For Additional Information on ACP or HLB

  • FDACS-DPI Huanglongbing/Citrus Greening Disease Information
  • UF IFAS Featured Creatures: Tamarixia radiata
  • UF IFAS Featured Creatures: Asian citrus psyllid
  • Know the quarantines in your area and learn to leave Hungry Pests behind.

  • Consult Federal and State websites for specific information and regulations. Contact the USDA Cooperative Extension Service in your area for further information.

  • Citrus plants sold in a regulated state must be sold from a certified vendor and be accompanied by a USDA certificate.

  • Commercial citrus businesses, internet shippers and roadside vendors within regulated states should be able to prove they are in compliance with the federal quarantine. Before you buy, ask the vendor if their product is in compliance.

  • The movement of branches, cut greens, green waste, dead trees and other regulated items will be regulated and enforced by federal, state and county quarantine officials.

  • Cut flower producers in quarantined areas are not affected unless they utilize Murraya, a host plant closely related to citrus, or flowers and branches cut from plants regulated for citrus greening and Asian citrus psyllid.

  • Within quarantine areas consume home-grown citrus fruit at home and do not transport home-grown citrus or citrus plants out of the area.

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